ILLINOIS BIRDS:A CENTURY OF CHANGE

Summary

Commissioned by the Illinois Natural History Survey, data compiled from bird counts at three fifty-year intervals, and repeated at the same locations, make up the oldest standardized survey in the nation.

A Century of Counts

From 1906 to 1909, in a first study of its kind, Alfred Gross, a University of Illinois graduate, along with his assistant Howard Ray, crisscrossed Illinois counting birds for the Illinois Natural History Survey (INHS). For three years, in all seasons, they traveled by whatever means possible—foot, train, horseback, steamboat—conducting transects across the southern, central and northern parts of the state, border to border. They compiled a species count of birds using a specific, repeatable method, forming a baseline for research and comparison in years to come.

Fifty years later, during the summers and winters of 1956 to 1958, husband and wife ornithologist team Richard and Jean Graber repeated these surveys. From 2006 to 2008, one-hundred years after the initial surveys, six naturalists retained by the INHS again conducted these surveys, adding point counts to their methodology. ILLINOIS BIRDS: A CENTURY OF CHANGE is a compilation of their research and a look back over time at land use changes and changes in bird populations.

This is a benchmark book because of the time period and geography covered. Though the research does not take into account all bird species and all locations, enough major bird groups were encountered to provide conclusions deemed reliable, along with implications and predictions for the future.

Research Methodology and Results

Evaluating changes in bird populations is challenging and complex. INHS chose to look at occupancy rates, measured as increasing, decreasing, or stable. Eighty percent of the 133 species detected were encountered often enough to estimate how their populations changed over time, and 73 sites in the state were used as a basis for comparison.

In these counts, the number of species observed during transect surveys rose from 93 in the 1900s to 128 in the 1950s to 133 in the 2000s. The most recent count included 26 species that weren’t found at all in the first, and only one that had disappeared, the Bachman’s sparrow. However, there were other species not found in the 2000s surveys that were found in the 1906- 09 surveys and are still seen in the state today, like the prairie chicken.

Though land use has changed substantially, and the human population has increased, one-third of the bird species surveyed had stable occupancy rates, and slightly more (40%) had increases rather than decreases. The northern region had the most stability (50%), and the central region had the greatest increases (46%). All three regions had roughly the same proportion of declining species, despite differences in landscape.

Bobolinks. Photo by Greg Massey. Courtesy of allaboutbirds.org.

Population and Land Use Changes

In the last century, Illinois’ population increased from five to 13 million. Urban and developed areas, with 85% of the population, are the fastest growing land use category.

There are 4.5 million fewer acres of pastures, hayfields and grasslands. Prairies, savannas, and shrublands have also declined. Acreage of corn and soybean row crops increased, with greater yields coming from the same acreages. Forests have gained some ground, mostly in southern Illinois, due to population loss and abandoned marginal croplands.

Factors Affecting Changes in Bird Counts

As land use changes, so do bird species. Shrubland and savanna birds like red-headed woodpeckers, brown thrashers, field sparrows and bobwhites have been in decline for a century. In the last fifty years, grasslands with meadowlarks, dickcissels, and bobolinks have given way to row crop fields with horned larks and blackbirds. Grassland ground-nesters like quail and pheasant are also among the “losers.”

Habitat quality and land management also affect birds. Habitat preservation and restoration are very beneficial. Illinois has preserved over 1.5 million acres of bird habitat (USGS 2010). The use of chemicals and pesticides less persistent than DDT, and improved water quality, has also helped sustain some species.

Notably however, are other factors influencing change. Among these are:

The introduction of species (exotics, invasives) from other areas;

Range expansions;

Climate change; and

Adaptation (the “wildcard ”)

Some species are better at adaptation than others, and these are going to “win ” out. Success favors the generalists, as opposed to the specialists. The implications of this are that the more we can do to preserve or create conditions preferred by the specialists, the more likely we are to avoid their extirpation.

Bird Findings

Over all three surveyed regions of the state, bird abundance has increased the most among four species: red-winged blackbirds, robins, starlings, and grackles. Seventy-six of the 133 species found now number one in a thousand, or rarer. The worst period for birds in Illinois was most likely between the late 1940s and early 1970s, when there was wider use of DDT and our waters were more contaminated. The Clean Water Act and the banning of DDT in the 70s has had a positive impact on raptors and fishing species like bald eagles, hawks, herons, and gulls.

While some species recovered following declines in the 50s, others did not, like the loggerhead shrike and Bewick’s wren. Once a population declines, other factors like habitat change or competition from other birds inhibits or prevents recovery. It is wise to prevent damage in the first place by controlling the use of chemicals and contaminants on habitats preferred by birds.

Introduced species have had some impact on bird counts. Eurasian collared doves and house finches have “invaded ” Illinois in recent decades. Like house sparrows and rock pigeons, these birds thrive in altered habitats, like urban areas. Climate is also expected to alter habitats and species in the coming century. Predictions are that by 2050, winters in northern Illinois will average 5 degrees warmer. By 2100, that temperature could increase to 10 degrees in the north and 5 in the south, making the climate in Illinois closer to that of northern Texas.

The authors have made some “guesses ” or choices as to the species most likely to increase in the next 50 years, and to disappear.

INCREASES

EXTIRPATED

Steve Bailey

Blue grosbeak

Common moorhen

TJ Benson

Red-shouldered hawk

Upland sandpiper

Jeff Brawn

Fish crow

Red-headed woodpecker

Jill Deppe

Trumpeter swan

Loggerhead shrike

Jeff Walk

Swallow-tailed kite

Bobolink

Mike Ward

Black-bellied whistling duck

Whippoorwill

How to Help?

According to the authors, the birds that need the most help are shrubland and grassland birds. While forest bird populations are generally in better condition, it is important to retain as many large tracts of old growth forest as possible, as they take a long time to acquire, and are not homogenous, therefore conducive to a variety of bird species.

Agricultural areas can help by not mowing ground covers during nesting seasons. Developed areas can help by planting trees and shrubs preferred by birds, and letting backyards get messy, for birds to take cover, particularly during migration periods.

Gail Goldberger, a former board member and former editor of The Compass, is a writer. Her work spans human services, health care, ecology, nature and the environment.

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